Analysis Tiphia parasitoids pre-ovipositional behaviors and of scarab host defensive responses

Tiphia vernalis Rohwer was introduced as a biocontrol agent against Japanese beetles (Popillia japonica Newman) and oriental beetles (Anomala orientalis). Several studies have shown that under field conditions, T. vernalis parasitize Japanese beetles more often than oriental beetles. This study was done to understand how Tiphiid wasps handle the two different host species and the influence of host defensive behavior on the oviposition success of Tiphiid wasps. The pre-ovipositional behaviors performed by Tiphia wasps included, stinging, examining, moving soil, kneading, host-feeding, and host scraping. The frequency, sequence, and total time spent on each behavior before oviposition were scored and compared between two host species. The sequence and frequency of preovipositional behaviors did not show a difference between the two host species. Although the overall host-handling time between the two host species did not show a difference, the wasps spent significantly longer time trying to sting oriental beetles than Japanese beetles. The defensive behaviors performed by Japanese and oriental beetle grubs included: vigorous movements, rubbing their abdomen or head against the wasp’s abdomen, and biting at the attacking wasp. The frequency, sequence, and total time spent on each defensive behavior was scored and compared between two host species. Oriental beetle grubs spent significantly longer time on defensive behaviors which likely cause wasps to spend longer time trying to sting oriental beetle grubs than Japanese beetles. The active host resistance gained through behavioral defenses could make oriental beetle grubs less susceptible to parasitoid attack than Japanese beetle grubs, especially under field conditions.